This invention relates to a flexible elastomeric sealing boot, for use in the annular space between a piston and cylinder of a disc brake assembly to protect the piston and cylinder chamber from contamination by dirt and water.
Disc brake boots, or dirt seals, are known and used in the automotive field. However, the known type of elastomeric rubber boot which is generally used is a boot having a uniformly thin flexible wall which is molded in an accordion-pleated, or bellows, collapsed form and then during operation is stretched into an elongated form for use in a dirt boot assembly with one end being retained in a recess of the cylinder bore wall and the other end being retained in a piston groove. In the interest of space and weight economy, the piston-to-recess annular space must be kept as narrow as possible. For example, the piston diameter may be 45 mm in outer diameter and the cylinder recess for retaining the boot, may be 58.3 mm in diameter. Also, the boot must be capable of extending approximately 30 mm and collapsing to an overall height of about 11.5 mm when the piston is retracted to change the brake pads. The resulting narrowness of the annular space between the retaining wall of the recess and the piston makes it very difficult to mold a boot of bellows configuration with its accordion-like convolutions having sharp bends. The convolutions are required to permit the conventional boot to flex and roll into the annular space upon retracting the piston. The sharp bends in the bellows wall of the prior art boot cause the boot to operate in an uneven, jerky manner during retraction and extension. A conventional type of convoluted boot having a bellows type sleeve is taught, for example, by Kondo, U.S. Pat. No. 3,998,466, issued Dec. 21, 1976.